Grease seal cup to retain lubrication for life extension in existing splined joint

ABSTRACT

A grease seal cup for a splined joint between a drive shaft and a driven shaft comprises a cylindrical portion adapted to form a seal with the outer surface of the drive shaft and a seal with a sealing member, such as a spanner nut, of the driven shaft. The grease seal cup, comprising a flexible polymer material, tightly squeezed during installation to form the seals. The pre-fabricated light weight grease seal cup can be used in existing splined joints without adversely affecting the weight balance.

GOVERNMENT INTERESTS

The invention was made with Government support under contract numberF33657-91-C-0006 awarded by Boeing Military Aircraft and is subject tothe provisions of that contract. The Government has certain rights inthis invention.

BACKGROUND OF THE INVENTION

The present invention generally relates to splined joints and, moreparticularly, to grease seal cups to retain lubrication for lifeextension in existing splined joints.

Splined joints are used in many devices for transmitting torque betweentwo components, such as a motor drive shaft and compressor shaft.Generally, a splined joint includes a series of internal splines formedon one of the components engaging a series of external splines formed onthe other of the two components. Typically, a splined joint is assembledby positioning the two components end-to-end lengthwise so that theinternal splines are circumferentially aligned with the spaces betweenthe external splines and then sliding the components axially intooverlapping engagement so that the two sets of splines become enmeshedwith one another.

A lubricating material, such as grease, may be provided at the interfaceof the internal and external splines to reduce component wear. Duringcomponent operation, the lubricating material tends to be removed fromthe spline interface due to centrifugal force. Additionally, somesplined joints are exposed to materials, such as hot hydraulic fluid,which also tend to remove the grease that is intended to lubricate thesplines. Without lubrication, the splines wear out prematurely and limitthe component service life. For some applications, the loss of splinejoint lubrication has limited component service life to ¼-life.

U.S. Pat. No. 4,281,942 provides a lubrication system for a splineconnection. The described system comprises a split ring at one end ofthe spline connection and a supply of oil at the other end. Duringoperation, centrifugal force pushes the two halves of the split ringapart, allowing the oil to flow through the spline connection and outthrough the split ring. A quad o-ring around the circumference of thesplit ring pulls the two halves together when the shaft is stationary,closing off the oil path. Although the disclosed system may providelubrication for a spline connection, the added weight of the heavy metalsplit ring may not be suitable for some existing applications. Forexample, applications including a Scotch yoke design require the weightbalance to be maintained and the incorporation of the heavy split ringmay necessitate a total redesign. Additionally, this lubrication systemdoes not sufficiently reduce lubrication loss due to hot hydraulic fluidexposure.

Japanese Patent No. JP11180259 provides a grease cup for a connectingshaft. The cup comprises a rigid washer positioned between a shaft and arotary lever. The rigid washer is bent upward during assembly tosuppress the outflow of grease from the area between the shaft and thelever and to prevent the inflow of water. Although the described greasecup may be used to reduce grease loss from the joint between a shaft anda lever, it may not have the symmetry necessary for use in a splinedjoint between two high-speed rotating shafts. Additionally, because thedescribed cup is formed during installation by bending the washer, itmay not be useful for applications requiring an easy to installpre-fabricated component.

As can be seen, there is a need for improved mechanisms to retainsplined joint lubrication. A lightweight apparatus that can maintain theweight balance of an existing system is needed. Additionally, anapparatus is needed that is pre-fabricated and easy to install.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an apparatus for a splined jointformed between a first component and a second component comprises acylindrical portion having an inner diameter adapted to receive thefirst component; and an end portion radially inward from and integral tothe cylindrical portion, the end portion having an opening adapted toreceive the second component.

In another aspect of the present invention, an apparatus for a splinedjoint formed between a drive shaft and a driven shaft comprises apolymer cup-shaped structure having a cylindrical portion and anopening; and a seal cup cavity radially inward from the cylindricalportion.

In still another aspect of the present invention, an apparatus for asplined joint of a compressor comprises a cylindrical portion positionedradially outward from the splined joint and radially inward from aspanner nut of the compressor such that the splined joint is sealed.

In yet another aspect of the present invention, an assembly comprises adriven shaft having a plurality of external splines; a drive shafthaving a plurality of internal splines in engagement with the externalsplines; and a grease seal cup positioned such that a cylindricalportion of the grease seal cup is radially outward from the drive shaftand radially inward from a sealing member of the driven shaft, saidcylindrical portion forming a first seal with the drive shaft andforming a second seal with the sealing member.

In another aspect of the present invention, an apparatus for a splinedjoint formed between a hydraulic motor shaft and a compressor shaftcomprises a cylindrical portion having an inner diameter adapted toreceive the hydraulic motor shaft and having a tapered outward surface,the cylindrical portion having an axial length of between about 0.273inches and about 0.283 inches, the cylindrical portion comprisingpolytetrafluoroethylene, the cylindrical portion adapted to form a firstseal with the hydraulic motor shaft and to form a second seal with aspanner nut of the compressor shaft; and an end portion radially inwardfrom and integral to the cylindrical portion, the end portion having anopening adapted to receive the compressor shaft, the end portion havinga thickness of between about 0.025 inches and about 0.031 inches.

In a further aspect of the present invention, a method of joining adrive shaft and a driven shaft comprises the steps of applying alubricant to the external splines of the driven shaft; passing thedriven shaft through the opening of a grease seal cup to position theexternal splines within the seal cup cavity of the grease seal cup; andaxially urging the drive shaft toward the driven shaft such that asplined joint is formed.

In yet another aspect of the present invention, a method of preventingloss of spline joint lubrication comprises the steps of forming a firstseal between a grease seal cup and a first component of the splinejoint; and forming a second seal between the grease seal cup and asealing member of a second component of the splined joint.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a grease seal cup installation accordingto one embodiment of the present invention;

FIG. 2 a is an isometric view of a grease seal cup according to oneembodiment of the present invention;

FIG. 2 b is a cross-section view through line 2 b of FIG. 2 a;

FIG. 3 is an exploded view of the grease seal cup installation of FIG.1;

FIG. 4 a is a cross-section view of a grease seal cup according to oneembodiment of the present invention;

FIG. 4 b is a cross-section view of a grease seal cup according toanother embodiment of the present invention;

FIG. 4 c is a cross-section view of a grease seal cup according toanother embodiment of the present invention;

FIG. 4 d is a cross-section view of a grease seal cup according toanother embodiment of the present invention;

FIG. 5 is a flow chart of a method for joining a drive shaft and adriven shaft according one embodiment of the present invention; and

FIG. 6 is a flow chart of a method for preventing loss of spline jointlubrication according one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

Broadly, the present invention provides grease seal cups to retainlubrication for life extension in existing splined joints and methodsfor producing the same. The grease seal cups according to the presentinvention may find beneficial use in many industries includingaerospace, watercraft, automotive, and electricity generation. Thepresent invention may be beneficial in applications including powertransmission for automobiles, aircraft and ships. This invention may beuseful in any splined joint application.

In one embodiment, the present invention provides a grease seal cup fora splined joint that connects a first shaft to a second shaft. The firstshaft, such as a hydraulic motor shaft, may have a plurality of internalsplines. The second shaft, such as a compressor shaft, may have aplurality of external splines. Unlike the prior art, the grease seal cupmay comprise a flexible polymer, such as Teflon®. The second shaft maybe positioned through an opening in the bottom of the grease seal cupand the first shaft may be urged into engagement through the top of thegrease seal cup. During the installation of the first shaft, thecylindrical portion of the grease seal cup may be squeezed between theouter surface of the first shaft and a component of the second shaft,such as a spanner nut, to seal the splined joint. The present inventionmay comprise a pre-fabricated cup-shaped apparatus that can be easilyinstalled on the second shaft. This is unlike the prior art thatrequires washer bending during installation. Because the presentinvention may comprise a light weight polymer cup-shaped structure, itcan be used in existing splined joints without adversely effecting theweight balance, which is also unlike the prior art.

A grease seal cup installation of the present invention is depicted inFIG. 1. A grease seal cup 40 may be positioned radially outward from asplined joint 44. The splined joint 44 may include a series of internalsplines 47 (see FIG. 3) formed on a first component 45 engaging a seriesof external splines 48 (see FIG. 3) formed on a second component 46. Thegrease seal cup 40 may form a first seal 60 a with the first component45 and form a second seal 60 b with a sealing member 58. The sealingmember 58 may be a structure of the second component 46 that is radiallyoutward from the splined joint 44, such as a spanner nut.

An embodiment of the grease seal cup 40 is depicted in FIGS. 2 a and 2b. The grease seal cup 40 may comprise a cylindrical portion 41 and anend portion 42. The end portion 42 may comprise an annular shaped memberhaving an opening 43 there through. The cylindrical portion 41 may beadapted to receive the first component 45. The opening 43 of an endportion 42 may be adapted such that the second component 46 may bepassed through the opening 43 for grease seal cup installation. The endportion 42 may be radially inward from and integral to the cylindricalportion 41 such that the circumference of the end portion 42 is incontact with the cylindrical portion 41. Radially inward may be definedwith reference to a longitudinal centerline 57 through the grease sealcup 40. The cylindrical portion 41 and the end portion 42 may define aseal cup cavity 49 for receiving the splined joint 44.

A diameter 51 a of the opening 43, depicted in FIGS. 2 a and 2 b, may beadapted to receive the second component 46. In other words, the diameter51 a of the opening 43 may be such that at least a portion of the secondcomponent 46 may be passed through the opening 43 to position theexternal splines 48 within the seal cup cavity 49. The diameter 51 a mayvary with application and may depend on factors including the dimensionsof the second component 46. For example, for some splined jointapplications, the diameter 51 a of the opening 43 may be between about0.395 inches and about 0.405 inches. A diameter 51 b of the end portion42, depicted in FIG. 2 b, may be such that the circumference of the endportion 42 is in contact with the cylindrical portion 41. A thickness 52of the end portion 42 may vary with application and may depend onfactors including the composition of the end portion 42. For somesplined joint applications, the thickness 52 may be between about 0.025inches and about 0.031 inches.

The cylindrical portion 41 may have a top end 55 and a bottom end 56, asdepicted in FIG. 2 b. The bottom end 56 may be integral to the endportion 42. The cylindrical portion 41 may extend axially from thebottom end 56 to the top end 55. An axial length 68 of the cylindricalportion 41 may vary with application and may depend on factors includingthe dimensions of the splined joint 44. For some applications, the axiallength 68 of the cylindrical portion 41 may be about equal to the axiallength of the splined joint 44. For some splined joint applications, theaxial length 68 may be between about 0.273 inches and about 0.283inches.

An inner diameter 50 of the cylindrical portion 41 may be adapted toreceive the first component 45. The inner diameter 50 of the cylindricalportion 41 may be about equal to a first component outer diameter 53, asdepicted in FIG. 3. For some splined joint applications, the innerdiameter 50 of the cylindrical portion 41 may be between about 0.565inches and about 0.575 inches.

As illustrated in FIG. 3, the cylindrical portion 41 of the grease sealcup 40 may have an inward surface 61 and an outward surface 54. Theinward surface 61 may conform to an outer diameter surface 59 of thefirst component 45 (see FIG. 3). The outward surface 54 of thecylindrical portion 41 may be adapted such that the grease seal cup 40may form the first seal 60 a with the first component 45 and form thesecond seal 60 b with the sealing member 58, as depicted in FIG. 1. Thesealing member 58 may be a structure of the second component 46 that isradially outward from the splined joint 44, such as a spanner nut. Thesealing member 58 may vary with application. For some applications, thesealing member 58 may comprise a spanner nut to retain the shaft sealand ball bearing in place.

The outward surface 54 may be adapted such that the cylindrical portion41 may be deformed during installation of the grease seal cup 40 to formthe seals 60 a,b (See FIG. 3). In one embodiment, the outward surface 54may be at an angle 62 to provide a tapered shape wherein an outerdiameter 63 a of the cylindrical portion 41 towards the top end 55 isgreater than an outer diameter 63 b of the cylindrical portion 41towards the bottom end 56, as depicted in FIG. 4 a. In other words, theoutward surface 54 may be tapered outward from the end portion 42. In analternate embodiment, the outward surface 54 may comprise a flange 66positioned towards the top end 55, as depicted in FIG. 4 b. In otheralternate embodiments, the outward surface 54 may comprise at least oneradially extending projection. For example, a plurality of ridges 64 orribs 65 may be positioned on the outward surface 54, as depicted inFIGS. 4 c and 4 d.

The outward surface 54 may comprise any outward surface that is tightlysqueezed during the installation of the grease seal cup 40 to providethe seals 60 a,b. The seals 60 a,b may physically prevent materials fromentering or exiting the splined joint 44. The seals 60 a,b may preventmaterials, such as hot hydraulic oil, from entering the splined joint44. The seals 60 a,b may prevent spline joint lubrication from beingremoved by centrifugal force during shaft operation.

The grease seal cup 40 may be installed by passing the second component46 through the opening 43 to position the external splines 48 within theseal cup cavity 49. The first component 45 may be urged axially towardthe second component 46 such that the splined joint 44 is formed. Achamfer 67 may be provided at the top end 55 of the inward surface 61 ofthe cylindrical portion 41 for ease of installation. The axial urging ofthe first component 45 may squeeze the cylindrical portion 41 betweenthe outer circumference surface 59 of the first component 45 and thesealing member 58. The flexible deformation of the cylindrical portion41 may provide the seals 60 a,b.

The grease seal cup 40 may comprise a flexible polymer material. Usefulflexible polymer materials may include polyamides, polyimides,elastomers, fluorocarbons, nylons, silicones, and polyvinyl and polyolefin compounds. Useful flurocarbons may includepolytetrafluoroethylene (Teflon®). Polytetrafluoroethylene may be aninert polymer that may be useful for applications exposed to hightemperatures and high pressures. Useful elastomers may includepoly(vinylidine fluoridehexafluoropropylene) copolymer (Viton®). Thegrease seal cup 40 may be formed by conventional methods, such asmachine cutting or moulding techniques. For grease seal cups 40comprising more than one material, convention composite mouldingtechniques may be useful.

The first component 45 may comprise any shaft having internal splines47. For example, the first component may comprise a drive shaft, such asa hydraulic motor drive shaft. The second component 46 may comprise anyshaft having external splines 48. For example, the second component 46may comprise a driven shaft, such as a compressor shaft.

A method 100 of joining a drive shaft and a driven shaft is depicted inFIG. 5. The method 100 may comprise a step 110 of applying a lubricantto the external splines of the driven shaft and a step 120 of passingthe driven shaft through the opening of a grease seal cup to positionthe external splines within the seal cup cavity of the grease seal cup.The method 100 may comprise a step 130 of axially urging the drive shafttoward the driven shaft such that a splined joint is formed. The step110 of applying a lubricant may comprise providing a grease to thesurface of the external splines. The step 130 of axially urging maycomprise squeezing the grease seal cup between an outer surface of thedrive shaft and a spanner nut of the driven shaft.

A method 200 of preventing loss of spline joint lubrication is depictedin FIG. 6. The method 200 may comprise a step 210 of forming a firstseal between a grease seal cup and a first component of the splinejoint, and a step 220 of forming a second seal between the grease sealcup and a sealing member of a second component of the splined joint. Thestep 210 of forming the first seal may comprise squeezing thecylindrical portion of the grease seal cup such that the inward surfaceof the grease seal cup contacts the outer circumference surface of thefirst component. The step 220 of forming the second seal may comprisesqueezing the cylindrical portion of the grease seal cup such that theoutward surface of the grease seal cup contacts a sealing member of thesecond component.

As can be appreciated by those skilled in the art, the present inventionprovides grease seal cups to retain lubrication in existing splinedjoints. The provided grease seal cups may comprise flexible polymer cupsthat may be easy to install. The grease seal cups may be used inexisting applications having a Scotch yoke design without adverselyaffecting the weight balance.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

1. A splined joint comprising: a first component and a second component;a grease seal cup having a cylindrical portion; a first seal formedbetween an inner diameter of said cylindrical portion of said greaseseal cup and said first component; a second seal formed between an outerdiameter of said cylindrical portion of said grease seal cup and aspanner nut of said second component; and an end portion radially inwardfrom and integral to said cylindrical portion, said end portion havingan opening adapted to receive said second component.
 2. The splinedjoint of claim 1, wherein said cylindrical portion comprises a flexiblepolymer material.
 3. The splined joint of claim 2, wherein said flexiblepolymer material is selected from the group consisting of polyamides,polyimides, elastomers, fluorocarbons, nylons, silicones, and polyvinyland poly olefin compounds.
 4. The splined joint of claim 2, wherein saidflexible polymer material comprises polytetrafluoroethylene.
 5. Thesplined joint of claim 1, wherein said first component comprises a driveshaft.
 6. The splined joint of claim 1, wherein said second componentcomprises a compressor shaft.
 7. (canceled)
 8. (canceled)
 9. The splinedjoint of claim 1, wherein an axial length of said cylindrical portion isabout equal to an axial length of said splined joint.
 10. The splinedjoint of claim 1, wherein an outward surface of said cylindrical portionis tapered.
 11. A splined joint comprising: a drive shaft; a drivenshaft; a polymer cup-shaped structure having a cylindrical portion andan opening; and a seal cup cavity radially inward from said cylindricalportion; a first seal between an inner diameter of said seal cup cavityand said drive shaft; and a second seal between an outer diameter ofsaid seal cup and a spanner nut of said driven component.
 12. Thesplined joint of claim 11, wherein said polymer cup-shaped structurecomprises polytetrafluoroethylene.
 13. The splined joint of claim 11,wherein said seal cup cavity is adapted to receive said splined joint.14. The splined joint of claim 11, wherein said opening is adapted toreceive said drive shaft.
 15. The splined joint of claim 11, wherein anend of said polymer cup-shaped structure distal relative to said openinghas a flange.
 16. The splined joint of claim 11, wherein an outwardsurface of said cylindrical portion has at least one radially extendingprojection.
 17. The splined joint of claim 11, wherein said radiallyextending projection comprises a ridge.
 18. The splined joint of claim11, wherein an axial length of said cylindrical portion is between about0.273 inches and about 0.283 inches.
 19. The splined joint of claim 11,wherein said polymer cup-shaped structure comprises nylon.
 20. Thesplined joint of claim 11, wherein said polymer cup-shaped structurecomprises an elastomer.
 21. A splined joint of a compressor comprising:a cylindrical portion positioned radially outward from said splinedjoint and radially inward from a spanner nut of said compressor; a firstseal between an inner diameter of said cylindrical portion and saidsplined joint; and a second seal between an outer diameter of saidcylindrical portion and said spanner nut.
 22. The splined joint of claim21, wherein said cylindrical portion has an axial length about equal toan axial length of said splined joint.
 23. The splined joint of claim21, wherein said cylindrical portion comprises a flexible polymermaterial.
 24. An assembly comprising: a driven shaft having a pluralityof external splines; a drive shaft having a plurality of internalsplines in engagement with said external splines; and a grease seal cuppositioned such that a cylindrical portion of said grease seal cup isradially outward from said drive shaft and radially inward from asealing member of said driven shaft; a first seal between saidcylindrical portion and said drive shaft; and a second seal between saidcylindrical portion and said sealing member.
 25. The assembly of claim24, wherein said drive shaft comprises a hydraulic motor drive shaft.26. The assembly of claim 24, wherein said driven shaft comprises acompressor shaft.
 27. The assembly of claim 24, wherein said grease sealcup comprises a flexible polymer material.
 28. A splined jointcomprising: a hydraulic motor shaft; a compressor shaft; a cylindricalportion having an inner diameter adapted to receive said hydraulic motorshaft and having a tapered outward surface, said cylindrical portionhaving an axial length of between about 0.273 inches and about 0.283inches, said cylindrical portion comprising polytetrafluoroethylene; afirst seal between said cylindrical portion and said hydraulic motorshaft; a second seal between said cylindrical portion and a spanner nutof said compressor shaft; and an end portion radially inward from andintegral to said cylindrical portion, said end portion having an openingadapted to receive said compressor shaft, said end portion having athickness of between about 0.025 inches and about 0.031 inches. 29-35.(canceled)